Safety joint



April 27, 1948. EDWARDS 2,440,257

SAFETY JOINT 'Filed Sept. 7, 1945 FIG. 2.

'. FIG. 3.

JNVENT LEWIS E. ED 0s ATTORNEYS Patented Apr. 27, 1948 sarn'rr JOINT Lewis E. Edwards, Huntington Park, Calli., as-

signor of forty per cent to Anthony J. Keel, Downey, and twenty per cent to'Louis Budway,

Huntington Park, Calif.

Application September 7, 1946, Serial No. 695,379 12 Claims. (01. 285-146) This invention relates, generally to devices for use in well drilling by the rotary drilling method and particularly to a safety Joint for incorporation in a string of drill pipe.

In drilling wells by the rotary drilling method, a bit is rotated at the lower end of a string of drill pipe which is made up of a number of pipe sections jointed together by coupling elements known as tool joints. Itis often desirable to be able to break, that is, unscrew, the pipe at a particular predetermined point in the string,

such as, for instance, in the event the bit becomes stuck during drilling. Without some sort of safety joint that will readily break or come apart more easily than the regular tool joints which are tightly made up as the drill pipe is run into the well, it is impossible to break or separate the pipe at the desired place. Such a Joint is useful also in a fishing string as well.

I am aware that various types of safety Joints have heretofore been devised and used, but so far as I know they have possessed disadvantages of one sort or another. Some, by reason of their construction, wear unduly and are short lived. Some cannot be depended upon to break, becoming too tight or impaired in their effectiveness by the drilling fluid or mud in the well working into or between parts of the joint. Others embody several working parts and often include an elongated spring element with the result that they easily get out of order and often break.

It is a primary-object of this invention to provide a novel safety joint of durable construction which, when installed in a string of pipe, provides a positive means of breaking or parting the drill string at a predetermined point.

It is also an object to provide a safety joint which is adaptable for use in a string of pipe under all conditions encountered in the use of a string of pipe in a well, including drilling and fishing operations. In this connection, it is an object to provide such a joint which is not affected by a longitudinal jarring of the pipe string, nor affected by compression or tension of the string, and which is effective to take the driving torque required for rotating the bit in drilling.

Another object of the invention is to provide a safety joint of simple construction having relatively few parts and no elongated spring elements.

It is a further object to provide a safety joint which oifers some resistance to being broken or unscrewed and thus can be used in a string of pipe where it is desired or necessary to operate a direction counter to that employed for drilling.

A still further object of theinventionis to provide a safety joint which cannot be overtightened.

These and other objects will be apparent from the following description and the accompanying drawing. Referring to the drawing, which is for illustrative purposes 'only: V

Fig. 1 is a fragmentary elevational view of an oil well showing the manner of incorporating the joint in a. string of pipe;

Fig. 2 is a longitudinal section of the joint with the parts positioned slightly spaced apart from the locked or fully tightened position;

Fig. 3 is a fragmentary elevation, partly in section, of the upper portion of the Joint taken on line 3-4 of P18- 2;

Fig. 4 is a cross section on line 4-4 of Fig. 2;

Fig. 5 is a cross section on line '5-5 of Fig. 2 and Fig. 6 is a cross section on line 6-6 of Fig. 2.

More particularly describing the invention, reference numeral It generally indicates the casing of a well and numeral [0 indicates a string of pipe suspended in the well by suitable means fragmentarily indicated at 12. Incorporated within the string of pipe Ii is the safety joint of my invention, which has been generally designated by numeral IS.

The upper end ,of the joint [5 is provided with a box or threaded socket It to receive a pin ll on the lower end of a section of the string of pipe ll, while the lower end of the safety joint is shown provided with a threaded pin l8 which may be screwed into a box Is at the upper end of the lower section of a string of pipe ll.

, Referring particularly to Figs. 2-6, inclusive, for a more detailed description of the invention, the safety joint i5 embodies what will be termed a mandrel member 22 which, as heretofore described, is provided with the socket it so that it may be attached to the ordinary pin of a tool Joint. The mandrel is tubular, being provided with a bore 23 extending therethrough to provide a passage for the circulation of drilling fluid commonly used in the drilling of oil wells and the like. Adjacent the lower end of the mandrel, there is provided an elongated threaded portion 24 which is adapted to thread or screw into a tubular member 26 which is provided with a bore 21 having screw threads corresponding to the threads on the portion 24. The tubular member 26 is provided with a fluid passage or tools in the string by a rotation of the pipe in II bore 30 which extends from the bare to the lower end of the member passing through the pin portion l8 heretofore described.

' In order to provide a fluid seal and prevent leakage of the drilling fluid into the region of the threaded connection 24-28 when the mandrel and the tubular member are secured together, the extreme end portion 32 of the mandrel is reduced in size and fitted with a pair of rings 33 and an annular packer 34 therebetween. These elements are held in place by means of a split ring 35 which is received within the peripheral groove 36 near the end of the mandrel. In order to make the packing effective, the tubular member 26 is provided with a smooth bore portion 38 below threads 28 which terminates at its lower end in a shoulder 39 against which the split ring 35 may abut to compress the packing. In this connection the groove 36 is sufliciently wide to permit of the longitudinal movement of the split ring thereon after the same engages the shoulder 39 as the parts are threaded together.

In order to provide resistance to relative rotation of the mandrel 22 and the tubular member 26 when the parts are threaded together, the mandrel is provided with an intermediate generally cylindrical section 42 which is interrupted by one or more slightly raised portions 43. These raised portions 43' may be formed by welding metal in the places shown and subsequently grinding or finishing the welds to'provide an outer arcuate surface thereon. The outer surfaces of these raised portions are spaced radially outward of the axis of the mandrel a distance equal to or very slightly greater than the radius of the smooth bore portion 45 at the upper end of the bore 21 in the tubular member so that the parts will have a friction fit.

The invention contemplates the provision of means for providing a flexible abutment or stop between the mandrel and the tubular member as the parts are threaded together and to provide means for ll'iOVii'lg the abutment means into firm engagement with the tubular member as the parts come together and the tubular member tends to rotate the abutment means on the mandrel. This abutment means comprises a sleeve 48 which is internally threaded and is fitted on a correspondingly threaded intermediate or central section 50 of the mandrel.

Preferably the threads on the mandrel and corresponding threads 52 in the sleeve are steeper in pitch than the threaded parts in the region 24, 28 and preferably the threads are of the square type and considerably larger. In addition, the threads 5! and 52 are normally left hand threads, but in any case are the opposite of the threads in the region 24, 23.

The relative rotation between the sleeve and the mandrel is limited by a flexible means comprising a longitudinally extending spring element in any other suitable manner in a slot 51 in the mandrel. The lower end of this spring extends into an elongated recess 58 in the upper end of the sleeve, the recess being flared at its uppe end.

With this construction, in the operation of the device the safety joint is adapted to be embodied in a string of pipe, such as, the string II, and the mandrel is attached to the lower end of a section of the string of pipe by means of the threaded socket it, while the lower end of the safety joint, that is the tubular member 25, is mounted at the upper end of a complementary 55, which is mounted by means of screws 56 or section of a string or pipe, suchas the lower portion of the string II. In order to make up or tighten the joint so that the string of pipe may be used for drilling a well or the like, the mandrel is threaded into the tubular member 26, the part or section 24 on the mandrel being received within the threaded bore portion 28 in the tubular member. When the parts have become sufllciently threaded one on the other to cause the upper end 60 of the tubular member to engage the lower end 6| of the sleeve 43, further relative rotation of the parts 22 and 26 will tend to cause the sleeve to be carried with the tubular member and move on the threads 5 I, 52 downwardly to more firmly engage the tubular member until further relative movement of the parts is prevented. This movement of the sleeve, of course, is extremely limited.

Once the parts have been secured together it is possible to rotate the string of pipe in a direction counterto the ordinary direction of rota-' tion used in drilling a well and to exert suflicient torque on the string to operate various tools which may be incorporated in the string of pipe and require such a counter rotation to operate. This is made possible by the raised portions 43 on the smooth section 42 of the mandrel which ofier a predetermined amount of resistance to the relative rotation of the mandrel and the tubular member.

Assuming that a bit becomes stuck in the hole and it is desired to disconnect it from the string of pipe, sufiicient torque is exerted on the drill pipe H to rotate the mandrel in a counterclockwise direction, that is, in a direction which will cause the mandrel to unscrew from the tubular member 26. As the mandrel is rotated, the threaded parts 5| and 52 tend to cause the sleeve 68 to ride up on the mandrel and away from the tubular member so that the end surfaces 60 and 6! on the tubular member and sleeve are disengaged and the mandrel may be readily unscrewed from the tubular member. Limited relative movement between the mandrel and the sleeve is permitted by the spring element 55.

Although the invention has been particularly shown and described, it is contemplated that various changes and modifications may be made and it isintended to cover such changes and modifications as come within the scope of the claims.

I claim:

1. A safety joint including, a tubular mandrel member adapted to be carried at the lower end of a string of pipe, a tubular member adapted to be carried at the upper end of a complementary string of pipe, means providing a threaded connection between said members, flexible abutment means carried by one of said members for limiting the extent of said threaded connection between said members, and means tending to urge said abutment means into firm engagement with the other of said members when said abutment means is engaged by said other member and tends to rotate therewith as said members are rotated relatively in a direction to screw one onto the other and tending to urge said abutment means out of engagement with said other member when said members are rotated relatively in an opposite direction.

2. A safety joint including, a tubular mandrel member adapted to be carried at the lower end of a string of pipe, a tubular member adapted to be carried at the upper end of a complementary string of pipe, means providing a threaded connection between said members, flexible abutment means carried by one of said members for limiting the extent of said threaded connection between said members, means tending to urge said abutment means into firm engagement with the other of said members when said abutment means is engaged by said other member and tends to rotate therewith assaid members are rotated relatively in a direction to screw one onto the other and tending to urge said abutment means out of engagement with said other member when said members are rotated relatively in an opposite direction, and flexible means for limiting movement of said abutment means.

3. A safety joint including, a tubular mandrel member adapted to be carried at the lower end of a string of pipe, a tubular'member adapted to be carried at the upper end of a complementary string of pipe, means providing a threaded connection between said members, a sleeve carried by said mandrel for engagement by said tubular member as it is threaded on said mandrel, and cooperative means on said mandrel and sleeve tending to urge said sleeve into firm engagement with said tubular member when engaged by same and tends to rotate therewith as said members are rotated relatively in a direction to screw one ontothe other and tending to urge said sleeve out of engagement with said tubular member when said members are rotated relatively in an opposite direction.

4. A safety joint including, a tubular mandrel member adapted to be carried at the lower end of a string of pipe, a tubular member adapted to be carried at the upper end of a complementary string of pipe, means providing a threaded connection between said members, a sleeve carried by said mandrel for engagement by said tubular member as it is threaded on said mandrel, interengaging cooperative helically disposed faces on said sleeve and said mandrel disposed in a direction opposite to the threads of said means forming a threaded connection, and flexible means limiting the extent of relative rotation permissible between said sleeve and said mandrel.

5.- A safety joint including, a tubular mandrel member adapted to be carried at the lower end of a string of pipe, a tubular member adapted to be carried at the upper end of a complementary string of pipe, means providing a threaded connection between said members, a sleeve carried by said mandrel for engagement by said tubular member as it is threaded on said mandrel, interengaging cooperative helically disposed faces on said sleeve and said mandrel disposed in a direction opposite to the threads of said means forming a threaded connection, flexible means limiting the extent of relative rotation permissible between said sleeve and said mandrel and means for effecting a seal between said mandrel and said tubular member when the same are threaded together in a region below said threaded connection.

6. A safety joint including, a tubular mandrel member adapted to be carried at the lowerend of a string of pipe, a tubular member adapted to be carried at the upper end of a complementary string of pipe, means providing a threaded connection between said members, a sleeve carried by said mandrel for engagement by said tubular member as it is threaded on said mandrel, cooperative means on said mandrel and sleeve tending to urge said sleeve into firm engagement with the other and tending to urge said sleeve out of engagement with said tubular member when said members are rotated relatively in an opposite direction, and means offering a predetermined first mentioned screw threaded portion, an internally threaded sleeve on said reversely screwthreaded portion of said mandrel, and means for limiting rotation of said sleeve relative to said mandrel.

8. A device as defined in claim 7 in which the threads of said reversely screw-threaded portion are of steeper pitch than the threads of said flrstmentioned screw-threaded portion.

9. A. safety joint including, a tubular mandrel member adapted to be carried at the lower end of a string of pipe, a tubular member adapted to be carried at the upper end of a complementary string of pipe, said mandrel being provided with an elongated screw-threaded portion at its lower end and said tubular member being provided with a correspondingly threaded bore for the reception of said mandrel, said mandrel having a reversely screw-threaded portion above said first mentioned screw-threaded portion, an internally threaded sleeve on said reversely screwthreaded portion, means for limiting rotation of said sleeve relative to said mandrel, and means on said mandrel engageable by said tubular member when said members are nearly threaded together for offering resistance to relative rotation of said members.

10. A safety joint comprising: an elongated tubular mandrel having an upper section adapted to be secured to the lower end of a string of pipe, having an upper screw-threaded portion below said upper section, having a substantially cylindrical face below said upper threaded portion, having a lower screw-threaded portion with the threads thereof disposed oppositely to the threads of the upper portion, and having a reduced lower end portion; an elongated tubular member adapted to be mounted at the upper end of a complementary string of pipe and provided with a bore having an intermediate screw-threaded portion adapted to thread onto the lower screwv threaded portion of said mandrel, packing means disposed around the reduced end portion of said mandrel for sealing the lower end of the mandrel in said tubular member; a sleeve mounted on the upper screw-threaded portion of said mandrel in position to ,be engaged at its lower end by the upper end of said tubular member when the same is threaded onto said mandrel; and a flexible retaining spring mounted in the upper section of said mandrel extending longitudinally thereof and engaging said sleeve, said sleeve being provided with a recess for the reception of said spring.

11. A device as defined in claim 10 in which the substantially cylindrical race of said mandrel is interrupted by raised portions adapted to frictionaliy engage the upper portion of the bore of said tubular member when the same is threaded onto said mandrel to said face.

12. In a. safety Joint, a tubular mandrel having a screw-threaded portion and a reduced cylindrical portion therebeiow at its lower end, said cylindrical portion being interrupted by an annular groove, a. tubular member having a screwthreaded portion tor the reception of the screwthreaded portion or said mandrel and havin: a cylindrical portion therebelow terminatinzin a. shoulder, packing means on said cylindrical portion oi. said mandrel, and a split ring in said groove adapted to bear against said shoulder to compress said packing means as the mandrel and tubular member are threaded together,

LEWIS E. EDWARDS. 

